Electronic devices such as computers, personal digital assistants (PDAs), radiotelephones, telecommunications equipment, servers and the like continue to evolve as manufacturers of such devices continue to improve the speed, size, functionality, battery life and longevity of these devices. In such devices it often useful to know how much current is being supplied by, or consumed by circuits, sub-circuits and components within the device. These components are typically mounted on a circuit board that interconnects the components utilizing copper planes or traces that are “sandwiched” between layers of insulating circuit board material. During the manufacture of circuit boards, the copper traces may be selectively etched from sheets of copper that are affixed to the insulating layers thereby forming traces.
There are many circumstances where it is desirable to accurately detect relatively high currents in a circuit to allow for better control of circuit operation. For example, controlling currents in a battery charging process can greatly increase battery life for battery powered devices. Determining if circuits or components are drawing excessive power can lead to measures that control these circuits such that they draw less power. Such control can greatly increase the reliability of electronic devices. Detecting current can also pinpoint systems and components that are malfunctioning or overheating and such systems can be shut down to avoid a catastrophic failure.
Traditional current sensing systems that sense relatively high currents introduce many design problems and have limited accuracy. For example, the power resistor typically utilized in current sensing systems may produce a significant voltage drop in the power line and may consume a significant amount of power. Thus, a designer may be faced with the design challenge of introducing an intrusive power loss and compensating for an intrusive voltage drop. The design challenges in current sensing technology have intensified with the new, low voltage standards. Some electrical components now require high currents at very low supply voltages. Current standards include, for example, power requirements of delivering currents of hundreds of amps at voltages of 1.8V, 1V, and below.